This invention relates to single heterostructure sawn cavity injection laser chip manufacture, and is particularly concerned with the obtaining of relatively narrow width emission regions in such devices.
The chip of a single heterostructure laser is typically in the region of 120 microns thick. The length of the optical cavity is typically in the region of 400 microns long, and the reflecting facets that define this cavity length are obtained by cleaving. In a conventional sawn cavity laser the remaining dimension of the chip, the width, is determined by sawing through the material of the semiconductor slice to divide up a bar semiconductor material into individual chips. By this method chips can readily be prepared with widths down to about 80 microns. However, it becomes increasingly difficult to produce satisfactory lasers with widths thinner than this. One of the factors responsible for this difficulty is the fact that the sawing process produces microcracks in the residual material adjacent the saw cut. It follows therefore that, if two parallel saw cuts are made sufficiently close together, the material between them is rendered mechanically weak when the microcrack propagation from one saw cut approaches, or even worse becomes interleaved with, microcrack propagation from the other.